Tap-hobbing machine



H. E. DURKEE TAP HOBBING MACHINE Feb. 4, 1930.

Filed Nov. 3. 1926 8 Sheets-Sheet A TTORNEY H. E. DURKEE TAP HOBBING MACHINE Feb. 4, 1930.

Filed Nov. 1926 8 Sheets-Sheet 2 mil/1L2 7 A TTORNEY Feb. 4, 1930. H, E, EE 1,745,750

TAP HOBBING MACHINE Filed'Nov. 1926 8 SheetsSheet 5 A TTDHNEY v Feb. 4, 1930. H. E. DURKEE TAP HOBBING'MACHINE 8 Sheets-Sheet Filed Nov. 1926 6 ZgE/ITOR A TTORNEf Feb. 4, 1930. H. E. DURKEE 1,745,750

TAP HOBBING MACHINE Filed Nov. 1926 8 Sheets-Sheet 5 A TTOHNEY H. E. DURKEE Feb; 4,1930.

TAP HOBBING MACHINE Fiied Nov. 5. 1926 8 Sheets-Sheet III 1/ 1 I 1/ INVENTOR J flflQM/l/QM A TTORNEY Feb. 4, 1930. H. E. DURKEE 1,745,750

TAP HOBBING MACHINE Filed Nov. 5. 1926 8 Sheets-Sheet 7 BY V/I nrronusr Feb. 4, 1930. H. E. DURKEE I TAP HOBBING MACHINE Filed Nov. 1926 8 Sheets-Sheet 8 A TTURNEI f .Patented Feb. 4, 1930 UNITED STATES PATENT OFFICE HENRY E. DURKEE OF GLASTON'BURY, CONNECTICUT, ASSIGNOR TO PRATT & WHITNEY COMPANY, OF NEW YORK, N.Y.,

A CORPORATION OF NEW JERSEY TAP-HOBBING MACHINE Application filed ovember This invention relates to, screw thread hobbing machines and in particular to an auto-' matic tap hobbing machine adapted to completely form the threadedportions of a tap after a suitably turned and fluted blank has vide an improved form of cam actuated means for moving the carriage and slide carrying 'the hob or cutter axially and transversely respectively during and in timed relation to the rotation of the work spindle.

Another object of the invention is to provide improved means to rotate the work spin- '20 dle alternately at slow and fast speeds during operation, the slow rotation of the spindle being variable in accordance with the character of work being performed and the 7 rapid rotation being used to rotate the work between the successive cutting operations on the tap blank to save a max mum amount of 7 time.

Another object of the invention is to provide special means for positioning the mechanisms of the machine after a blank has been completely formed, to facilitate mounting a new blank in position, and to position the mechanism for a successive operation upon a new blank. I

Another object of the invention is to rotate the work spindle at an extremely slow rotative speed through a differential driving mechanism and to provide means to drive the spindle directly, the differential driving mechanism being adapted to be eliminated.

Another object of the invention is to provide auxiliary cutter carriage advancing mechanism enabling a second or finishing operation to be performed upon the same blank without varying the adjustments of the carriage controlling mechanism for a particular size.

A still further object of the invention is to provide improved automatic mechanisms for timingthe operation of the cutter and blank ,3, 1926. Serial No. 145,979.

a tap hobbing machine adapted to operate an tomatically after a tap blank has been placed" in position, but itwill be understood that certain features of the invention can be otherwise embodied and that the drawings are not to be construed as defining or limiting the scope of the invention, the claims ap ended to this specification being relied upon or thatw purpose.

In the drawings:

- Figure 1 is a plan view of a complete machine incorporating the present invention.

Fig. 2 is a front elevation of the complete machine, certain parts being broken away to more clearly show their construction.

Fig. 3 machine.

Fig. 4'is a horizontal sectional view of the headstock taken through the axes of the work spindle and lead cam spindle. I Fig. 5 is a transverse vertical section taken through the headstock of the machine substantially upon line 5--5 of Fig. 4.

Fig. 6 is a transverse vertical sectional view of another portion of the machine, the section being taken'substantially upon line 66 of Fig. 2. v

Fig. 7 is'a transverse sectional view taken through the headstock substantially upon line 77 .of Fig. 4.

Fig. 8 is a vertical sectional view through the headstock taken substantially upon line 88 of Fig. 4 and showing the controlling mechanism for starting operation of the machine and for varying the speed of rotation of the work spindle.

Fig. 9 is -a fragmentary front elevation partly in section of a portion of the driving.

mechanism for the machine.

Fig. 10 is a transverse sectional view of {s a rear elevation of the complete fourth, a lead cam rotatably the work spindle driving mechanism shown in Fig. 7. Y

Fig. 11 is substantially upon line 11-11 of Fig. 3.

Fig. 12 is a fragmentary side elevation of a detail of the mechanism for advancing the cutter carriage slightly to effect a second or finishing operation upon the blank, and

Fig. 13 is a detail sectional view on an enlarged scale of the shaft pivotally supporting the relieving cam lever. a

In the above mentioned drawings 1' have shown but one e'mbodimentof the invention which is now deemed preferable, but it is to be understood that changes nd modifications may be made within the scope of the appended claims without departin from the spirit of the invention.

Briefly, and in its broadest aspect, my invention comprises the following principal parts: First, a'base; second, a headstock rigidly mounted thereon; third, a work supporting and rotating spindle in said headstock;

mounted adj acent said headstock and adapted to be rotatedin timed relation to said spindle; fifth, means "described. ably on an integral upwardly extending porto rotate the work spindle at different speeds; sixth, means to control the rotation of the lead cam; seventh, a saddle adj ustably mounted upon the base; eighth, a longitudinally movable slide on said saddle and adapted to be reciprocated b the lead cam; ninth, a transversel mova 1e slide on said longitudinally mova le slide; tenth, a rotatable cutter spindle having a cutter thereon mounted on said transversely movable slide; eleventh, a tailstock 'adjustably mounted on said base for supporting an outer or free end of work mounted in the spindle; and twelfth, means to control the position of the longitudinal and transversely movable slides in timed relation with the rotation of the work spindle.

Referring more in detail to the figures of thedrawings, I provideabase 10 having atone end a headstock 11 preferably rigidly secured to said base 10 in fixed position. Within this headstock 11 is rotatably mounted a work supporting and rotating spindle 12 having chucking means 13 to engage and clamp one end of a work blank W mounted therein. Also mounted within the headstock 11 is a spindle 14. on which is mounted, adjacent one end, a lead cam 15 having a peripheral cam groove 16. The mechanism for controlling the rotation of the work spindle 12 and lead cam spindle 14 and'also for actuating the chucking means 13/011 said spindle 12 will presently be Mounted on the base 10, prefertail block 17 having an oscillamember 18 adapted to be moved, as by means of the lever 19, shown in Fig.1, into and out of position in alignment with the work-spindle 12. In operative position this center. member 18 engages and suption 16, is a tory tailstock center a transverse vertical section taken ports mounted within the work spindle 12.

Also mounted on a horlzontal surface on said base 10 is a saddle member 20 preferably adapted to be clamped to this horizontal surface on the base 10 by means of screws 21 shown in Figs. 1, 2 and 3. In order to adjust the angular position of this saddle 20 so that ahob or cutter 22 mounted thereon may be positioned precisely in parallelism with the the, outer free end of a work blank W I Work spindle 12, the saddle 20 is provided with elongated openings 23 at one end adapt-:

ed to be engaged by two of the screws means-of a small adjusting screw 24 attached to the saddle 20 and a hand nut 25 rotatably 10, the angular position of this saddle 20 may be adjusted wit in. a limited range. Mounted on this saddle 20 for longitudinal movement relative to the work spindle 12 is a slide or carriage 26 having a roller 27 projecting therefrom adapted to engage the peripheral groove 16 in the lead cam 15 so that as the lead cam 26 will be actuated longitudinallyin accordance therewith. As the longitudinal position of the carriage 26 must be widely varied for operations upon blanksW of different length and type, the roller 27 is not mounted directly upon the slide 26 but upon the end of a rod 28. The rod 28 by means of clamping screws 29 may be adjustably secured in;any ongitudinal position to the carriage 26.

Mounted on the suitable interen aging transverse ways being provided there or. A transverse screw 31 mounted for rotation within the longitudinally movable carriage 26 engages a nut 32 fixed within the transversely movable slide 30 so that the position of the transverse slide may be manually adjusted by means of a hand mg the cutting operation and during the rotation of the work spindle 12, a cam 37 is provided as shown in Fig. 11. This cam 37 through appropriate levers forces the screw 31 axially to effect the relieving movements of the cutter 22. The means to rotate this cam 37 will presently be described. 3

On the forward portion of this transverse slide 30 are provided suitable bearings within which is mounted a cutter spindle 38 on which may be mounted the hob or other form of thread cutting cutter 22 adjacent one end. Also an adjustable support 39 may be mounted on this transverse slide 30 having a'center longitudinally movable carriage 26 is a transversely movable slide 30,

mounted in a pro ection formed on the base the rod 99 and the yoke member 98 are in 0 At the rear end of this transverse shaft 82 1s a gear 92' mounted for ready removal and substitution of other different sized gears which is adapted to rotate an intermediate gear 93 which in turn rotates another change gear 94 on the rear end of a second transverse shaft 95. On this second .transverse shaft 95 is a worm 96 meshing directy with a worm wheel 97 keyed to the work spindle 12. It will be seen, therefore, that when theclutch 90 is out of its driving position the work spindle 12 may be rotated at any number of different extremely slow'speeds through the differential mechanism depending upon the change gears 92 and 94 positioned upon the rear erfds of the transverse shafts 82 and 95. With the clutch 90 in its operative or engaging position the spindle 12 is rotated at different relatively, high speeds. The clutch 90 is adapted to be moved back and forth between its engaged and disengaged position by'means of a yoke member98 engaging a circumferential groove in the. clutch 90 and movable with axial movements of a transversely extending rod 99.' Normally the rod 99 is forced by spring 100-in a direction to hold the clutch 90 engaged with the sleeve 81 and is adapted to be forced in one direction by oscillatlon of a lever 101 attached atits upper end to the rear end of a rod 102 directly in rear of rod 99. Means to actuate this lever to actuate the'clutch 90 in proper timed relation to the rotation of the work spindle 12 comprise dogs 103 ad1ustably mounted on a disk 104 keyed to a longitudinal shaft 105 in rear of the machine.

this shaft 105 at a higher speed than the work The means to rotate spindle 12 will presently be described. By reference to Fi 8 the operation of the oscillating lever. 10 to actuate the clutch 90 will be clear. The rod 102 has a member 107 thereon adapted to engage a catch 106which, when a position to disengage the clutch 90, retains them in that position. Movement forward of the rod 102-causes the member 107 to release the catch 106 from a member 108 on the rod 99 so that the rod 99 can move forward thus advancing the clutch 90 to engaged positions. Bearward movement of the rod 102 forces the member 107 against a collar 109 on the rod 99, thus forcing the rod 99 rearmeshing ward to disengage the clutch 90 and engag the catch 106 with member 108. 6

Also adapted to be driven from the first transverse shaft 82 is the lead cam 15 and its spindle 14 referred to above. In order to rotate this lead cam spindle 14 a worm 110 isprovided on the first transverse shaft 82 with a worm wheel 111 formed upon a sleeve 112 rotatable upon the spindle 14 so that when this sleeve 112 is drivingly conuected to the lead cam spindle 14 the lead cam 15 will be rotated slowly relative to the work spindle 12. a

The worm wheel 111 surrounding the lead relieving cam cam spindle14 is mounted at one end of thesleeve 112 at the opposite end of which is a seconddisk 113 carrying a pawl 114. Adja- "cent the disk 113 carrying the pawl 114 is a ratchet wheel 115. Rotation of the worm wheel 111 through the pawl 114 rotates the ratchet wheel 115 which is keyed directly to the lead cam spindle 14. During rotation of the work spindle 12 through the mechanism above described the lead cam 15 is rotated', the relative speeds being variable by slide 30 is actuated toward and from the axis upon which the work blank W is rotated a plurality of times during each rotation of the work spindle 12. In order to effect this movement of the transverse slide 13 the relieving cam 37 referred to above is mounted on abracket 116 outstanding from the rear wall of the base 10, and is ada ted to be driven by gear connections fromthe headstock 11. For this purpose the second'transverse shaft 95 within the headstock 11 is provided with aworm 117 keyed thereto in mesh with a worm wheel 118' on a short shaft 119 having a change gear 120 mounted on its outer end. This latter gear 120, through an intermediate gear .121, drives a change gear 122 on the outer end of the longitudinal shaft 105 rotatably mounted within the rear of the base 10. Atthe opposite end of this shaft 105 is provided a gear 123 meshing with a similar gear 124 on a short shaft 125 mounted upon the bracket 116 referred to' above. It is this latter shaft 125 which carries the relieving cam 37 which, as shown, is of spiral form. The cam 37 rotates in the direction indicated by the arrow in Fig. 11.

In order to move the transverse screw 31 and the slide 30 carrying the cutter 22 short distances by means of this cam 37, a lever 126 is mounted on the bracket 116, the lower arm of which carries a pin 127 adapted to engage one arm of a. bellcrank 128. The upper arm of the bell crank 128 has a contacting portion adapted to engage the periphery of the spiral 37. The upper end of the lever 126 bears against the end of the rod carrying the screw 31 andduring rotation of the cam 37 and therefore oscillation of the lever 126 this screw 31 is bodily forced forwardly durnormally urges the transverse silde 30 toward belts 41 from a niotor 42 conveniently mount ed within the base 10 of the machine and having a pulley 43 on its armature shaft. As the longitudinal position of the carriage 26 and therefore of the pulley 40 varies, means are provided for simultaneously moving the driving motor 42 for the cutter spindle 38 whenever adjustments are made in the longitudinal position of the slide 26. L

In order to effect this simultaneous, adjustment of the longitudinally movable carriage 26 and the cutter driving motor 42 by hand, a pinion shaft 44 is mounted for rotation about a fixed axis upon the base 10, a crank 45 being mounted on this shaft 44 for rotating it. A pinion 46 thereon meshes with a rack 47 on the longitudinal slide 26 so that by operating the crank 45 the slide 26 may be positioned to any desired longitudinal position. Also on this pinion shaft 44 is a bevel gear 48 meshing with a bevel gear 49 on the upper end of a vertical shaft 50. The lower end of this vertical shaft 50 is also provided with a bevel gear 51 keyed thereto and mesh-' ing with a bevel gear 52 on a short transverse shaft 53 rotatably mounted within the base -10 and carrying a pinion 54. This pinion 54 is movable carriage 26. On this slide 56 is mounted the driving motor 42 for the cutter 22. From this construction it will be seen that manual rotation of the upper pinion haft 44 will simultaneously advance the car:

riage 26 carrying the cutter 22 and the slide 56 carrying the driving motor42 so that the drivingpullev 43 and driven pulley 40 will always be maintained in proper relative posi-,

tion. 7

As the lead cam 15 is rotated simultane- 'ously with thework spindle 12 during'the cutting operations it will beseen that the longitudinally movable carriage 26 will be ading threaded will presently be described.

11 order to rotate-the work spindle 12 and the lead cam 15 a separate motor 60 is provided conveniently mounted within the base 10 below the headstock 11. This motor 60, by means of a belt 61, drives a pulley 62 on a driving shaft '67 positioned on the front of the base 10 directly below the headstock 11 (see Figs. 2 and 9). On this driving shaft 67 is a gear 68 meshing with another gear 69 on' a shaft 70 longitudinally mounted within the headstock 11. A clutch 71 keyed to but slidably mounted on this shaft 70 enables a helical pinion 72 to be rotated when the clutch 71 is in its driving position relative to a sleeve 73 to which the pinion 72 is keyed. To actuate the clutch 71 a push button 74 shown in Figs. 2 and 8 is provided, movement inward of which releases a catch 75 and permits a spring 76 to force the clutch member 71 to a position engaging teeth on the ing the cutting operation the work spindle 12 is driven at an extremely 'slowrotative Epeed. For this reason the gear 80 is not irectly connected to the transverse shaft 82 during the cutting operation but through mechanism most clearly, shown in Figs. 7 and 10. On the sleeve 81 carrying the gear 80 and which is rotatably mounted on the .shaft 82 is a double pinionmember, the pin ions 83 and 84 of which have a slightly different number of teeth. This member comprising pinions 83 and 84 is mounted on a vstud 85 outstanding from the gear 80 and forms the driving member of a differential mechanism. This, through intermediate gears 86 and 87 co-axial with the shaft 82, rotates the gear 86 which is direetlykeyed to the transverse shaft 82. The other of the pinions 87 mounted co-aXially with the transverse shaft 82 is keyed to-a member 88 rotatable on the shaft and having ratchet teeth on its periphery. It will be seen from the above that when the ratchet wheel 88 is retained from rotation as by means of a pawl 89 and the differential pinion members 83 and 84 is rotated and due to the difference in number of teeth on its pinions and on the pinions 86 and 87, the pinion 86 keyed to the transverse shaft 82 will be slowly rotated. To rotate the transverse shaft 82 at a higher speed in order to rotate the work spindle 12 between successive cutting operations, on a blank W a clutch 90 is mounted on the transverse shaft 82 movable into and out of engaging positionwith clutch teeth 91 formed on the face of the sleeve 81 carrying the helical gear 80. With the clutch 81 in its operative or engaged position the shaft 82 is directly driven from the gear 80 and the differential mechanism ratchets over.-

maintains the distance between the end ofmember 130 and the face of the nut 32 at all times constant,

From the above it will be seen that during rotation of the work spindle 12 the relieving cam 37 will be rotated in timed relation to the rotative movement of th work spindle 12, the ratio between the rotation of the cam 37 and work spindle'12 being changeable by the gears 120 and 122 driving the longitudinal shaft 105. This ratio is usually three to one or four to one and corresponds to the number offlutes formed in the tap blank W. The

relieving cam 37 makes as many revolutions per revolution of the work spindle 12 as there are flutes. In addition to its relieving movements the transverse slide 30 is adapted to be manually adjusted for differences in diameter of the cutter 22 and work W being operated on. For this purpose the shaft 34 carrying the gear 36 meshing with gear 35 on the transverse screw 31 is provided with the hand lever 33 and graduated dial.

The above described mechanism includes that usedfor actuating the cutter 22 during the normal operation of cutting threaded portions on a tap blank W. It is frequently desirable to take a second out upon a tap W and for that reason means are provided for continuing the rotation of the work spindle 12 through a second revolution while the lead cam spindle14 continues to rotate through another portion of its revolution. For this 1 purpose the dog 77 adapted to trip the lever I intermediate shaft 137 havinganother gear I so 7 9 and stop operation of the machine by disengaging clutch 71 is car'ried upon'it's disk'78 rotatable upon the work spindle 12. This disk 7 8 is ada-ptedto be driven therefrom at one-half the speedof the work spindle 12. Referring to Fig. 4, the means to drive this disk 7 8 are clearly shown. A gear 135 keyed to the work spindle 12 drives a gear 136 on an 138 formed directly thereon. This second gear 138 is in mesh with a larger'gear 139 keyed to and rotating with the disk 78. The ratio of this gearing "is such that two revolutions of the .work spindle 12 are required to rotate the disk? 8 through one complete turn. It will be seen, therefore, withone dog 77 on the disk 78 two revolutions of the work spindle'12 will be required before the dog 77 comes into contact with the latch 79 and releasesthe driving clutch 71 from, its operative pos1t1on. Should it be desired to merely take one out upon a tap W two dogs 77 may be mounted upon the disk 78 'at diametrically oppositebe performed upon the same blank W it is desirable to slightly advance the transverse slide 30 a very slight amount. For that purpose the lever 126 is carried upon a short shaft 140 having an eccentric .portion 141, the eccentric portion engaging and forming the pivot for the lever 126. By oscillating this shaft 140 by means of a hand lever 142 keyed to one end through a fraction of a revolution, the pivot forthe lever 126 will be moved forwardly a very small amount, thus advancing the slide 30 a corresponding amount.

In order to facilitate removing a finished tap W and setting-up operations when a new blank is about to be placed in the work engaging and chucking means 13 on the spindle 12, mechanism is provided for first opening the collet chuck 13, moving the transverse slide 30 to a rear position, and rotating the lead cam 15 towards its initial position. Then when a new blank W has been inserted in the collet 13, the collet is closed, the transverse slide 30 moved forward again to operative position and the rotation of the lead cam 15 continued until it is again in its initial position. The mechanism is then again in position for cutting operations.

F or this purpose a special driving member 145 is provided comprising a worm 146 thereon. This shaft or driving member 145 is driven by the main drive shaft 67 for the head-stock mechanism by gears 147 and retates a worm wheel 148. This worm wl eel 148 operates a ratchet wheel 1,49 continuously and rotates a gear 150 half revolutions when a lever 151 is manually actuated. This mechanism is similar in every way to that described in' my copending application Serial No; 88,471 filed February 15, 1926 and therefore a complete description is not thought necessary. By actuating the hand lever 151 in front of the machine in one or the other direction one of a pair of oppositelydisposed engaging lugs 152is moved to an inoperative position permittinga spring pressed pawl 153 carried by the gear 150 to engage the ratchet wheel 149 and rotate this gear 150 and its shaft 154 until the engaging lug 152 on the opposite side withdraws the pawl 153 from its engaging position whereupon the gear 150 stops rotation. This rotative movement of the gear 150 moves a crank 155 on the rear end of shaft 154 through a one-half revolution and therefore reciprocates a connecting rod 156,

one end of which is attached to this crank 155. Movement of the lever 151 in the opposite direction disengages the opposite lug 152 and thus permits the crank 155 and the shaft 154 to rotate another half revolution. Another connectingrod 157 is attached to the crank 155 @XtQIlding in the opposite direction from the connecting rod 156. The first movement of the connecting rods 156 and 157 is adapted to open the collet 13, withdraw the transverse slide 30 and the cutter 22 from operative position, and start rotation of the cam spindle 14 to advance the cam 15 towards its initial position.

The opposite end of the connecting rod 156 is provided with rack teeth and engages a pinion 160 keyed to a transverse shaft 161 within the base 10 which at its rear end is /provided with a bevel gear 162. The bevel gear 162 meshes with-a corresponding bevel gear 163 on a short longitudinally extending shaft .164 in rear of the base and carrying a. cam 165; A transverse view of this cam 165 and its associated parts is shown in Fig. 11.

. It will be seen that when the cam 165 is in the position shown in Fig. 11 the upper arm of the bell crank 128' is forced to an outer 1 position which moves the lever 126 toa position forcing the transverse slide 30 to its forward or operative positionthrough the lever 126 engaging the screw 31. During the setting-up operation, the first movement of the crank 155 rotates the transverse shaft 161 so that the cam 165 shown in Fig. 11. is rotated through a one-half revolution, thus bringing the screw 166. adjusted within the lower end of the bell crank 128 into contact with a portion of the periphery of cam 165 of less radius. This permits the transverse slide 31 to move rearwardly under the influence of the helical spring 129 and permits the upper end of the bell crank 128 to enter a suitably formed notch in the relief cam 37.

Similarly the half rotation of the disk and crank moves the second connecting rod 157 attached at one end to the crank 155 in a direction to oscillate the collet actuating lever 168 to'open the collet 13 thus permitting removal of the finished tap W and adapt it for insertion of a new blank.

In order to re-position the lead cam 15 for a second blank W, the first and second half rotative movements of the crank 155 are utilized, the mechanism for this purpose being shown clearly in Figs. 4, 5 and 6. The gear 150 carrying the awl 153 is in mesh with a gear 170" on the ront end of a short transverse shaft 171' having a bevel gear 172 on its rear end. This bevel gear. 172 meshes with a corresponding ear 17 3 on the lower end of a vertical sha t 174 extending upwardly entirely through the headstock 11. On an intermediate portion of this vertical shaft 174 is a spiral gear 175 in mesh with a i larger spiral gear 176 rotatively mounted coaxially with the lead cam spindle 14. Outstanding from the face of this spiral gear 17 6 is a stud 177 adapted to contact with a stud 178 on the ratchet wheel 115 previously referred to. It will be seen from this construction that when the rotative movement of the work spindle 12 and lead cam 15 stops at the completion of the operative movements of these parts and it is required to position the cam 15 for a new operation, the rotation of the vertical shaft 17 4 will rotate the spiral gear 17 6 and its stud 17 7 which in turn will contact with stud 17 8 and rotate the ratchet wheel 115 and the lead cam spindle 14 from whatever intermediate position in which it may have stopped at the completion of the cutting operation. The second rotative movement of the crank 155 again rotates the vertical shaft 174 and still further rotates the lead cam spindle14 through the studs 177 and 17 8 and the ratchet wheel 115 which keyed to the spindle 14.- Thespiral gear 176 rotates through exactly'one complete revolution by the combined rotative movements of the crank 155 and from any position of the stud 178 assumed at the end of the cutting operation the stud 177 on the spiral gear will pick up this stud 178 and rotate the lead cam spindle 14 from any intermedif ate position and advance it to its initial position. As soon as the cam spindle 14 is again in its initial position, a detent 180 is adapted. to move forward in engagement with anotchl in a disk 181 attached to and rotating with. the gear 17 8. The second half rotative move ment of the crank 155 moves the connecting rod 156 in' the rever direction and again rotates the cam 165 a half revolution to position' the bell crank. 128 for cutting opera.- tions'. also the connecting rod 157 is moved in the opposite direction to oscillate the lever* 168 to again close the collet chuck 13. v All of the mechanisms are then in position for cutting operations u on a new blank when by again pressing't e starting button 74 the cycle of operations above described is lever in one direction adapted to withdraw said cutter from its operative position and open said work engaging means, and move ment of said lever in the opposite direction adapted to return said cutter to its operative position and close said work engaging means.

2. A thread hobbing machine comprising in combination, a base, a headstock thereon, a

comprising work supporting and rotating spindle therein, a carriage on said base slidable in a direction ,rgarallel to said s indle, a transversely mova 1e slide on said rst slide, alead cam rotatably mounted adjacent said headstock, means to rotate said cam and said spindle in timed relation to ea other, means connecting said cam and Ian 'tudinally movable. f

carriage,a work engaging collet in said spindle, means to operate the above mentioned elements in accordance with a predetermined cycle, and manually controlled means to actuate said collet, move said longitudinally movable carriage, said transversely movable slide and rotate said lead cam.

A thread hobbing machine comprising in combination, a base, a headstock thereon, a work supporting and rotating spindle therein, a cutter supporting carriage slidable longitudinally on said base, cam means toadvance said carriage in timed relation to the rotation of said spindle, a transversely movable slide on said carriage, a lever pivotally mounted on said base and adapted to engage said slide, cam meansadapted to oscillate said lever to actuate said slide toward and from said spindle in timed relation to the spindle rotation, and means to vary the position of said lever on said base to sli htly advance said slide toward said spindle whereby a second cutting operation can be taken upon the same blank.

4. A thread hobbing machine comprising in combination, a base, a headstock thereon, a

- work supporting and rotating spindle therein, a cutter supporting carriage slidable longitudinally on said base, cam means to advance said carriage in timed relation to the rotation of said spindle, a tranversely movable slide on said carriage, a lever pivotally mounted on said base and engaging said slide, cam means adapted to oscillate said lever to actuate said slide toward and from said spindle in timed relation to the spindle rotation, and an eccentric mounting for said pivot for said lever avhereby rotation of said eccentric will vary the position of said lever to slightly advance said slide toward said spindle whereby a second cutting operation can be taken upon the same blank.

5. A thread hobbing machine comprising in combination, a base. a headstock thereon, a work supporting and rotating spindle therein, a cutter supporting carriage slidable longitudinally on said base, cam means to advance said carriage in timed relation to the rotation of said spindle, a transversely movable slide on said carriage, a lever pivotally mounted on said base and engaging said slide, cam means adapted to oscillate said lever to actuate said slide toward and from said spindle in timed relation to the spindle rotation, means to vary the position of said lever to I slightly advance said slide toward said spindle whereby a second cutting operation can be taken upon the same blank, and independent manually operated means to adjust said slide.

6. A thread hobbing machine comprising in combination, a base, a headstock thereon,

a work supporting and rotating spindle therein, a cuttersupporting carriage slidable longitudinally on said base, cam means to advance said carriage in timed relation to the rotation of said spindle, a transversely movable slide on said carriage, a lever pivotally mounted on said base and engaging said slide, cam means ada ted to oscillate said lever to actuate said sli e toward and from said spindle in timed relation to the spindle rotation, means to vary the position of said lever to slightly advance said slide toward said spindle whereby a second cutting operation can be taken upon the same blank, independent manually operated means to adjust said slide, and power operated means to retract said slide to an inoperative position.

. 7. A thread hobbing machine comprising in combination, a base, a headstock thereon, a work supporting and rotating spindle therein, means to rotate said spindle, a cutter supporting carriage slidable longitudinally on said base, a transversely movable slide on said carriage, a cutter on said transversely movable slide, cam means to actuate said slide toward and from said spindle in timed relation to the spindle rotation, and means driven by the work spindle at a reduced speed therefrom to stop rotation of said spindle and movement of said transversely movable slide after two complete rotations of said spindle.

8. A thread hobbing machine comprising in combination, a base, a headstock thereon, a work supporting and rotating spindle therein, means to rot-ate said spindle, a cutter supporting carriage slidable longitudinally on said base, a transversely movable slide on said carriage, a cutter on said transversely movable slide. cam means to actuate said slide toward and from said spindle in timed relation to the spindle rotation, and a dog wheel driven by gears from said spindle to stop rotation of said spindle and movement of said transversely movable slide after two complete rotations of said spindle.

9. A thread hobbing machine comprising in combination, a base, a headstock thereon, a

work supporting and rotating spindle therein. means to rotate said spindle, a cutter supporting carriage slidable longitudinally on said base, a transversely movable slide on said carriage, a cutter on said transversely movable slide, cam means to actuate said slide toward and from said spindle in timed relation to the spindle rotation, and a disk mounted coaxially with and by said spindle at a reduced speed relative thereto to stop rotation of said spindle and movement of said transversely movable slide after two complete rotations of said spindle.

In testimony whereof, I hereto afiix my signature.

HENRY E. DURKEE. 

